capriccio, caprice, capriccioso, capricieux, capricieuse—a short character piece, typically in a humorous, fanciful, or playful manner. The concept juxtaposes the improvisatory free-form fantasy against the more formal, "serious" and logically "worked-out" sonata forms.Within a caprice, the range of expression may well include the serious and dark as well as demanding extraordinary technical skills such as a prelude or etude.

intermezzo, intermedio [S], intermède [F], interlude, Entr'acte—music that is "inserted" (or "interpolated) between two musical entities of greater importance (e.g. movements, acts, verses, etc.). Often suggests music of a lighter character, entertaining contrast or even improvisation.

quartet, quatuor [F], quartett [G], quartetto [I]—ensemble or work for four players the most important examples being the string quartet and the piano quartet

spirito, con spirito, spiritoso, spirituoso—Spirited, lively

string quartet, Streichquartett [G], quatuor à cordes [F], quartetto d'archi [I], quartetto di cordi [I]—an ensemble as well as music written for that ensemble comprising 2 violins, viola and cello. This is one of the essential genres / forms / ensembles of chamber music and arguably a critical "core" of "classical" music. Explore the string quartet.